Tetracyclines: Uses, common brands, and safety info

Tetracyclines are systemic, broad-spectrum antibiotics that treat a variety of types of bacterial infections as well as chronic conditions related to the presence of bacteria, such as acne and rosacea. Tetracycline antibiotics date back to the 1940s and have been used to treat infections in both humans and animals. Only certain types of bacteria are susceptible to tetracycline antibiotics, meaning tetracyclines are not appropriate for all infection types. 

The first tetracycline to be discovered was in 1948 by Benjamin Duggar and was called Aureomycin (chlortetracycline). The second tetracycline was called Terramycin (oxytetracycline) was brought to market by Pfizer in the 1950s. These drugs are no longer on the market, but there are currently four tetracycline antibiotic derivatives available on the United States drug market.  Tetracycline is a naturally occurring molecule derived from Streptomyces bacteria. Doxycycline, minocycline, and demeclocycline are semisynthetic tetracyclines that were later developed. 

Antibiotics generally fall into one of two categories, bacteriostatic or bactericidal. Bacteriostatic implies that the antibiotic inhibits further growth of the bacteria. Bactericidal implies that it kills the bacteria. Tetracyclines are generally bacteriostatic. Due to the fact that tetracyclines have been in use for an extended time and the fact that they are bacteriostatic, there is some concern about antibiotic resistance to tetracyclines. Antibiotic resistance occurs when bacteria are able to adapt to survive and grow despite the presence of antibiotics. This concern about resistance has led to decreased tetracycline usage for certain conditions, though tetracyclines remain a mainstay treatment for other types of conditions. Only your healthcare provider can determine if tetracycline treatment is appropriate for you. We will discuss the various properties, common brand names, and safety of tetracyclines here.

Other tetracyclines

• Dynacin (minocycline)

• Adoxa (doxycycline)

What are tetracyclines?

Tetracyclines are a class of antibiotics used in the treatment of various types of infectious diseases. They were first discovered in the 1940s, deriving from the Streptomyces bacteria. Microorganisms, or bacteria, that are typically susceptible to tetracyclines include gram-positive and gram-negative bacteria, chlamydiae, mycoplasma, protozoans, and rickettsiae. Bacterial resistance has become a concern with tetracyclines as their mode of action helps stop the continued growth of bacteria and other pathogens, however, it does not necessarily kill the organism.

Tetracyclines are sometimes used when bacteria have become resistant to other first-line treatment protocols or when drug allergies prevent the use of preferred treatments. One example is the treatment of methicillin-resistant Staphylococcus aureus, oftentimes referred to as MRSA. There is some evidence that a community-acquired MRSA infection that is not susceptible to drugs such as penicillin may be sensitive and treatable with a tetracycline drug such as doxycycline. Only laboratory tests can confirm the sensitivity of any given organism, but tetracyclines may be an option in some treatment plans when other antimicrobials are not effective. Tetracyclines may also be considered when an allergy to penicillin exists. 

How do tetracyclines work?

Tetracyclines are generally bacteriostatic due to their mechanism of action. They bind to the ribosomal subunit which acts as a messenger for DNA during protein synthesis. This ribosome binding causes inhibition of protein synthesis which stops bacterial cell growth. At very high concentrations, tetracyclines are bactericidal, meaning they will actually kill the bacteria. Although tetracyclines are still in use today, the concerns about resistant bacteria have limited their use due to concerns about effectiveness. The mechanism of action makes tetracyclines useful in both the treatment and prophylaxis (prevention) of many conditions.

What are tetracyclines used for?

• Malaria

• Anthrax

• Acne and moderate to severe acne vulgaris

• Rosacea

• Diseases of the gum

  • Ulcerative gingivitis

  • Listeriosis

• Genitourinary tract infections

  • Syphilis

  • Gonorrhea

  • Chlamydia

  • Bacterial urinary tract infections

• Gastrointestinal  infections

  • Choler

  • Campylobacter (food poisoning)

  • Intestinal amebiasis

• Respiratory infections

  • Pneumonia

  • Psittacosis

  • Upper and lower respiratory tract infections

• Skin and skin structure infections

• Rocky Mountain spotted fever

• Tick bites

  • Lyme disease

Types of tetracyclines

First generation

Tetracycline is a naturally occurring tetracycline derived from Streptomyces aureofaciens, Streptomyces rimosus, and Streptomyces viridofaciens. While tetracycline was very effective as an early oral antibiotic, improvements were sought in the later development of tetracyclines to enable intravenous administration and improve absorption when given orally.

Demeclocycline is also a first generation tetracycline. This drug is unique because it possesses diuretic properties which make it useful in conditions such as hyponatremia. However, due to factors such as inconsistent time to onset of action, it is not widely used.

Second generation

Doxycycline and minocycline are second generation semisynthetic tetracyclines. Both drugs are available for oral and parenteral administration.

Who can take tetracyclines?

Adults

Adult men and women can take tetracyclines. If a patient has ever had a known hypersensitivity reaction to a tetracycline antibiotic, then all tetracyclines should be avoided. 

Seniors

If an older patient has renal impairment or decreased kidney function, excessive amounts of tetracyclines may accumulate as they are excreted by the kidneys. Doxycycline appears to be less impacted by kidney function and may be the safest choice in a patient with decreased renal function. Dosing in senior patients may need to be adjusted for both kidney and liver function.

Children

Tetracyclines may have a significant effect on the bones and teeth of young children. They may cause permanent yellow or brown discoloration to the teeth. The use of tetracyclines in children under the age of 8 should be avoided.

Are tetracyclines safe?

Tetracyclines recalls

• Avet PharmaceuticalLabs Inc.: Low out of range dissolution results, April 2020

Tetracyclines restrictions

Do not take tetracyclines if you have a history of hypersensitivity reaction to any antibacterial in the tetracycline class.

Tetracyclines are contraindicated in children under 8 due to their permanent negative effects on bone structure. The only exception would be treating malaria or anthrax if no other options are available.

Patients with renal impairment or hepatic impairment may have to avoid tetracyclines or have their dosages adjusted to account for the decreased drug clearance. 

Tetracyclines can cause photosensitivity. Patients taking tetracyclines who are exposed to UV light are at an increased risk for sunburn and other skin reactions. Direct UV light should be avoided when taking tetracyclines.

Tetracyclines are inactivated by calcium, magnesium, aluminum, and other cations. Therefore tetracyclines should not be taken with milk, yogurt, other dairy products, and most over-the-counter antacids. 

Almost all antibiotic therapy, especially broad-spectrum antibiotics such as tetracyclines, carry a risk for the development of pseudomembranous colitis caused by an organism known as Clostridium difficile. This is sometimes referred to as c.diff. The effects of tetracycline antibiotics in the gastrointestinal tract can disrupt the natural balance of bacteria which are always present in the stomach. This can lead to an overgrowth of certain organisms such as Clostridium difficile. This condition can range from mild to life-threatening. It is characterized by diarrhea and stomach pain most often. If you begin experiencing these adverse events while on a tetracycline antibiotic, please notify your healthcare provider immediately.

When you are prescribed antibiotics of any type, including tetracyclines,  you must follow your doctor’s order and take it exactly as prescribed. Discontinuing an antibiotic regimen early, or missing doses can lead to tetracycline resistance. This is where the bacteria or microorganism being treated learns to adapt and thrive in the presence of the antibiotic. This can lead to the drug or drug class not being effective against current or future infections. Antibiotic resistance is a major concern in the practice of medicine as there are organisms where we already have very few options for drug treatment. Not all tetracyclines will be dosed the same. The pharmacokinetic profiles of the different tetracyclines affect how they will be dosed. For example, doxycycline may be dosed once or twice daily depending on the dose and the condition being treated due to its longer half-life. Some dermatology specific formulations of doxycycline, such as Oracea, are formulated for once-daily dosing, while other formulations like Vibramycin are typically dosed twice daily.

Can you take tetracyclines while pregnant or breastfeeding?

Tetracycline is categorized as category D by the Food and Drug Administration (FDA). The use of tetracyclines should be avoided in pregnant and breastfeeding women. All tetracyclines have been shown to have a detrimental effect on the skeletal development of a fetus or child.

Are tetracyclines controlled substances?

No, tetracyclines are not controlled substances.

Common tetracyclines side effects

The use of tetracyclines, as well as most antibiotics, carries the risk of some adverse effects. These may vary slightly. For example, this class of antimicrobial medications in general causes many gastrointestinal side effects such as nausea and loss of appetite. This may be alleviated by taking the dose with food. As an exception, doxycycline does not necessarily have to be dosed with food and is generally regarded as being easier to tolerate. Some side effects may not occur with short durations of treatment but may become more noticeable with longer treatment periods or higher doses.

The most common side effects for tetracyclines include:

• Acid reflux

• Diarrhea

• Nausea

• Vomiting

• Stomach cramps

• Decreased appetite

• Headache

• Photosensitivity reactions

• Sunburn

• Pigmentation changes/ discoloration of the skin

• Discoloration or staining of the teeth

• Skin rash

• Itching

• Sore mouth or tongue

• Vaginal itching

• Vaginal discharge

• Tinnitus (ringing of the ears)

• Fatty liver

• Intracranial hypertension

How much do tetracyclines cost?

Most tetracycline formulations are available generically. Through the use of free coupons provided by SingleCare, many tetracyclines are very cost effective. For example, a typical 10-day course of generic doxycycline can be as low as $4 through the use of a SingleCare coupon. In contrast, a newer extended formulation of doxycycline known as Oracea is very expensive. Even in its generic form with a SingleCare coupon, you may still pay anywhere from $500 to $700 for a one-month supply. 

Your insurance may have formulary restrictions which will suggest that you try regimens of certain preferred drugs first before they will approve the use of more expensive medications to treat your condition. Before filling your tetracycline medication, always check with SingleCare to make sure you are paying the best price.